The exhaust gas from the internal combustion engine contains harmful substances such as carbon monoxide, hydrocarbons, nitrogen oxides, fumes and particles of lead and lead compounds, and sulfur dioxide, which cause public nuisance.
In the conventional internal combustion engine where the filter extends perpendicular to or across the main axial direction of the exhaust pipe, a fine mesh filter results in a high back pressure in the exhaust and accordingly in a drop of the engine shaft output and its power; and if the filter mesh is broadened to reduce the back pressure, the contact between the filter and the exhaust gas for adsorption and reaction decreases, resulting in deterioration of the purifying effect of the filter.